Binaries for `fuzzit.dev`

[HeroicKatora]

I've been contacted by fuzzit.dev and they have been generous enough to provide us with 4 cpus for fuzzing 24/7. This opens up the question for payloads and/or corpus. The integration on their side is largely based on libfuzzing/cargo-fuzz. It is possible to switch the binaries at any time. Integration of regression tests with the corpus into CI would also be useful, automatic creation of fuzzing binaries requires use of a private API key of course and could be done for the master branch at fixed intervals as well (there's a cronjob on Travis for image for example).

@fintelia Due to this being an administrative action. Also, I should add you to the organization on fuzzit. Gitter for chat if there are questions besides the decision of fuzzing binaries.

[HeroicKatora]

For the moment, I've decided on image-png as a test ground considering:

• There are no concerns over resource exhaustion since it has a Limits api
• Its fuzzing integration already exists
  • It checks limits manually, maybe that should be improved
• It has an extensive corpus. Naturally from pngcheck + some automatically generated cases from previous, manual fuzzing runs.
• A manual run for ~1 hour did not turn up any immediately obvious issue
• There was a previous regression that would have been avoided through rigorous testing of the whole corpus